Electrical testing apparatus.



H. J. BLAKESLEE.

ELECTRIGAL TESTING APPARATUS.

APPLIOATION FILED PEB. 23, 1909.

Patented Mar. 1, 1910.

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rit-.artnr a. nnnnnsnnn, or srnacnsnnnw renin ELECTRICAL TESTING APPATUS.

Specification of Letters Patent.

Patented Mar.. i, 191..

Application filed February 23, 1909. Serial No. 479,489.

.To all whom it may concern:

Be it known that lt, HENRY lLAnnsnnn, of Syracuse, in the county of tlnondaga, in the State of New York, have invented new and useful Improvements in Electrical Testing Apparatus, of which the following, taken in connection with the accompanying drawings, is a full, clear, and exact description. Y

This invention relates to certain improvements in apparatus for testing electric meters and analogous instruments, but more particularlyfor testing Watt,V hour meters.

ll am aware that in making the latter, tests it is customary to use a portable load con-l sisting of lamps or other translating devices which not only consume an electrical energy equal to that registered by the meter under test, but in testing the larger metersl these energy consuming devices either become too bulky for convenient portability and ,manipulation or operate at too high a temperature for safety. ln testing alternating current watt hour meters l find that this consumption of energy is unnecessary providing Vthe current coils of the meter under test and standard meter are supplied in series with an alternating current from any source under such conditions that the potential stresses, phase relations and Wave forms are equivalent to those obtaining under normal methods of testing. rlhese equivalent conditions maybe obtained by the use of an alternating'current transformer having its primary winding supplied -With the same potential which is impressed upon the meter, and the secondary supplying current to the current coils of the meter under test and standard meter.

My main object, therefore, is to provide a more etiicient and .practicable meter testing apparatus comprising a simple, compact and easily portable transformer of small Watt capacity and preferably ofthe strictly potential type in which the core magnetization may be constant.

yAnother object is to obtain control over the secondary current throughout the entire range of its capacity through the medium of suitable contacts which may be easily and quickly adjusted thereby economizing in time and labor in making the necessary thor ough tests.

Thev object in using a former as distinguished from the so-called current transformer is to obv'iate the use of delicate resistance in series with a primary in order to obtain complete regnlationY of the secondary current and at the same time to avoid varying magnetic densities and also vary-ing and uncertain Wave forms in the secondary circuit incidental to the use of such resistance in the primary, thereby obviating the relatively small noninduc'tive resistance and consequent'increased lag of the secondary current. ln other Words l have sought to eliminate any resistance as such in series with the primary, allowing the transformer to operate under constant magnetization for all loads and permitting control of the secondary by noninductive resistance inseries with the meter coils, thereby reducing the lag of the secondary current to a negligible quantity by introducing a poperly designed resistance in shunt with the secondary Winding of the transformer, or rather by connecting ondary winding whereby any amount of current from zero to the maximum capacity of the transformer may be obtained by connecting one of the contacts to different points of the resistance, and the other contact to dierent points of the secondary Winding, thus obviatingpthe use of a much higher resistance which otherwise would be necessary, and which would also necessarily be eitherl too fragile or bulky, or both, to accomplish the same control. l

A still further object is to utilize the resistance coil as a handle by which the transformer may be conveniently carried from place to place.

@ther objects and uses will be brought out in the following description:

ln the drawings-Figure 1 is a diagrami maticview of a watt-hour meter under test. g a standardized meter and my improved testing apparatus electrically connected to said meters. Fig. 2 is a perspective view of the detached testing apparatus exclusive of the felectrical connections and contacts. Figs. 3

potential transand 4 are res ectively longitudinal and transverse vertica sectional views taken through the testing apparatus shown in Fig. 2 taken on lines 3-3 and 4--4 Fig. 2. Fig. 5 is a perspective View of the detached secondary winding of the transformer. Fig. 6 is a perspective view of one of the laminas of the same transformer. Fig. 7 is an elevation of the detached contact plug. l

In illustrating the operation of my invention -I have shown diagrammatically in Fig. l a working circuit -1- in which are connected potential coils or windings -2- and -3- of a meter -4- under test and a standardized meter -5- respectively, the series or"current coil of the meter under test being connected in the usual manner in seriesfwith one side of the working circuit, while the series or currentcoil of the standardized meter is adapted to be connected in series with the secondary winding of my improved testing apparatus presently described, and is, therefore, indirectly connected in series with. the saine side of the working circuit-as the current coil-of the meter under test.'

The testing apparatus comprises in this y instance an alternating current potential transformer consisting of a laminated core -6-, a primary winding -7-, a secondary coil 8 and an external resistance coil 9+ which is connected across and in shunt with a ortion of the secondary winding -8, as st seenfin Figs. 1, 2 and 3, all of said parts being brought together incompact size and form and inclosed Within a suitable-house or -casing -10- to conceal and protect the major ports of the transformer, thereby constituting a comparatively small and easily portable testingapparatus.

The core -,-6' com risesa suitable number of thin magnetiza le frames or laminae arranged side by side in close proximity and provi ed with central tongues 1l-.- upon which the primary coil -7- is Wound, leaving'suitable openings -12- of ample size to receive said primary and secondar coils.

The primary winding 7 pre erably consists of a large number of turns of comparatively small wire having its ends secured to suitable terminals 1S- which are adapted to be connected by wires 43'- across the working circuit -1- between the source of electric energy and meter -4- under test, although in some instances the primary may be connected to some other suitable source of electric energy if desired.-

The secondar winding -8- surrounds the primar win ing and preferably consists of aV smal number of turns of comparatively coarse low resistance conducting material, such as cast brass or copper, passing through the openin 12- in the core, each turn being provided withv one or more apertures nected, but

-14- preferably in opposite ends thereof and'registerng with similar openings -15- in the adjadent sides of the inclosing case f-lO- for the reception of a contact termina-l or plug -16.

The resistance coil -9- referably consists of a sfuitabl'elength ofp comparatively coarse German silver or' equivalent wire having its opposite ends electrically connected across. a portion of the secondary coil -8-, and in order that this resistance coil may perform its electrical. function and at the'same time serve as a convenient handle'by which the transformer may be easily carried from place to place the ends of the coil are firmly secured in suitable metal conducting plates -17- which in turn are secured to the top of the case -10- by suitable fastening means, as screws -18-, and

.are electrically connected to one side of one of the turns of the secondary coil -8- by screws #-19- thereby affording a secure anchorage for the. resistance coil or handle 9 and at the same time permitting said coil to be readily removed or replaced when necessary. This resistance coil 9 is of such design and construction as to carry thc whole or any part of the secondary current of the transformer without excessive heat- Iing, and at the saine time is sufiiciently rugged and durable to permit it to b'e used as a handle for carrying the transformer from place to place, said resistance being adapted to be connected to the external circuit in which the meter under test is located by means of an adjustable contact member -20- and wire -21,' the contact member being movable into and out of contact with any one of the turns of 'the coil 9 as may be necessary in testing the, meter -4-. In like manner the contact plug -16- may be connected at different points to any one of the turns of the secondary coil -8- and is-in this instance connected by a wire Q2- throu h the series coil, as

Q4- of the standar meter to the same side of the working circuit in which the series coil ofthe meter under test is conreferably between the meter and load, suc as translating devices -25-. By connecting the resistance -9- in the manner described across a portion of the secondary winding, a close local circuit is formed including the resistance and that portion of the secondary winding between the points of connection with the resistance due to the electromotive force in that part of the winding. The resistance must, therefore, be sufficient to reduce the local current in the closed local circuit to a negligible value.

In order that the load of thetranslating devices Q5- may be cut out during the testing-` operation, I provide the working asoma circuit -1 with a switch4 -A4- which, in this instance, is shown as located between the translating devices --25- and meter under test.

llt is now apparent that -When the transformer is connected in the manner described,

' with the specially designed resistance coil ondary Winding, any amount `of current from zero to the maximum capacity of the transformer may be passed through the apparatus under testl by simply connecting the contact members to different points of the resistance and to dierent points of the secondary Winding, thereby obviating excessive weight and .bulk and keeping the resistance and heat under maxlmuin current tests to a minimum or safe degree. It is also apparent that by connecting the transformer to the Working circuit in the man;4 ner shown and described, the primary circuit of the transformer is supplied with 'the same potential Which is impressed upon the meter, and by-sliifting the contact members -l6 and 20-,- into and out of contact with different points or turns of their respective coils, any amount of current from zero to the maximum capacity of the transformer may be impressedI upon both meters simultaneously, thereby assuring a thorough and ractical test of the Watt hour meter or ot er apparatus under test, and enabling such test to'be made quickly and economically and Without special skill in the art of handling such apparatus. e

ltn making the test it is simply necessary to connect the potential coil of the standard meter -5 across the Working circuit 1 and to similarly connect the primary Winding of the transformer across the sameA working circuit or to any other suitable source of electrical energy and to then place the contact members -16-- and .-20- in contact with the desired points of the secondary Winding 8*- and resistance coilv -9 respectively, the positioning of the contact members -16- and 20- depending entirely upon the amount of current required to make the desired test, the secondary current being controlled by electrically connecting the contact members to dierent points of their respectiveeoils, the condition of the meter under test being determined by comparing its registration with that of the standardized meter -5-. lit is evident. however, that the mechanical elements and electrical connections of the testing apparatus are susceptible to many moditications within the scope of my invention, and, therefore, I do not limit myself to the precise construction and arrangement shown and described.

What ll claim is l. lin an electrical testing apparatus, a

` transformerhaving' a handle of electric conp connected toits secondary Winding. -9 connected across a portion of the secl 3. ln an electrical testing apparatus, a

I transformer having an electrical resistance connected in shunt to its secondary Winding in combination with an external circuit having adjustable contacts with the resistance andv secondary Winding respectively and including a portion of the instrument under test.

4. lin an electrical testing apparatus, an alternating current transformer having an electric conducting handle consisting of a resistance coil connected in shunt to a portion of its secondary Winding.

5.111 an electrical testing apparatus, an alternating current transformer a fixed resistance connected across a portion of the transformer, and an external circuit having a contact member making contactwith the secondary Winding of the transformer and an additional contact member contacting with the resistance. l

6. An alternating current transformer havin recesses in different portions of'its secon ary Winding, and means for entering said recesses and making a slip contact with the adjacent portion of the secondary Windin ln an electrical testing apparatus an alternating current transformer having an electrical resistance electrically connected across a portion of its secondary Winding, and an external circuit having separate contact members movable to make contactwith different portions of the resistance and with different points in the secondary Winding respectively.

8. lin an electrical testing apparatus, a transformer having at least some of the turns of its secondary Winding provided 4With apertures, an external circuit including a' portion of the instrument under test and a plug adapted to be insertedin either of said apertures and having contact with the secondary Winding and a resistance connected across a portion of and to said circuit. p

9. ln an electrical testing apparatus, a transformer, a resistance connected at tivo points to a portion of the secondary of the the secondary Winding transformer and constituting a closed cir-' cuit, and a separate circuit including therein a portion of the instrument under test, a portion of the secondary Winding and a ortion of the resistance and also including leads to such instrument, one of said leads being connected to the `:secondary of the transformer and the other lead to a point on ico said resistance between the two first mention of the instrument under test, and leads `tioned points. thereto, one of said leads being connected to 10. In an electrical testingapparatus, a the secondary and the other lead connected transformer, a resistance, two points of to said resistance at a point between the two 15 which are connected to the secondary of said A first mentioned oints. transformer and constitute a closed ci'rcuit In .Witness` w ereof I have hereunto set including such resistance and the portion of my hand this 18th dayy of February, 1909. the secondarywinding of the transformer HENR J. BLAKESLEE.

between such points, and an additional cir- Witnesses: cuit connecting afortion of said secondary H. E. CHASE and resistance an also connected to apor- Jnssm M. Hons. 

